Ultra-high temperature fracturing fluid

Abstract

An ultra-high temperature fracturing fluid, including the following components in mass percentages: 0.4 wt %-0.8 wt % of a polymer thickener, 0.015 wt %-0.02 wt % of a non-metallic crosslinking agent, 0.04 wt %-0.06 wt % of a gel breaker and the rest is water. The polymer thickener is obtained by a polymerization of acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, rigid monomer and cationic hydrophobic monomer in a weight ratio of 55-70:15-20:15-20:0.5-3:0.1-1.0, the polymerization temperature is 30-40 C. and the polymerization time is 8-10 hours. The fracturing fluid of the present invention can effectively solve the technical problems that traditional fracturing fluids are easily decomposed at high temperatures and affect performance.

Claims

1. A fluid, comprising the following components in mass percentages: 0.4 wt %-0.8 wt % of a polymer thickener, 0.015 wt %-0.02 wt % of a non-metallic crosslinking agent, 0.04 wt %-0.06 wt % of a gel breaker, and rest of the fluid is water; wherein the polymer thickener is obtained by a polymerization of acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, rigid monomer and cationic hydrophobic monomer in a weight ratio of 55-70:15-20:15-20:0.5-3:0.1-1.0; wherein the gel breaker is an ammonium persulfate capsule and/or ammonium persulfate; and wherein the rigid monomer is N-vinyl-2-pyrrolidone and/or sodium p-styrenesulfonate.

2. The fluid according to claim 1, wherein the fluid comprises the following components in mass percentages: 0.6 wt % of the polymeric thickener, 0.015 wt % of the non-metallic crosslinking agent, 0.04 wt % of the gel breaker, and the rest of the fluid is water.

3. The fluid according to claim 2, wherein the non-metallic crosslinking agent is polyethyleneimine.

4. The fluid according to claim 1, wherein the non-metallic crosslinking agent is polyethyleneimine.

5. The fluid according to claim 1, wherein the cationic hydrophobic monomer is at least one selected from the group consisting of dimethydiallyllammonium chloride, [2-(Methacryloyloxy)ethyl]trimethylammonium chloride and dimethyl octadecyl allyl ammonium chloride.

6. The fluid according to claim 1, wherein the polymer thickener is prepared by the following method: acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, rigid monomers and cationic hydrophobic monomers are mixed and polymerized at a temperature of 30-40 C. for 8-10 hours to obtain a copolymer; then the copolymer is crushed, dried and finally pulverized.

7. A method of fracturing stimulation of ultra-high temperature wells, the method comprising: using a fluid in the fracturing stimulation of ultra-high temperature wells at temperatures of 180-260 C., wherein the fluid comprises the following components in mass percentages: 0.4 wt %-0.8 wt % of a polymer thickener, 0.015 wt %-0.02 wt % of a non-metallic crosslinking agent, 0.04 wt %-0.06 wt % of a gel breaker, and rest of the fluid is water; wherein the polymer thickener is obtained by a polymerization of acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, rigid monomer and cationic hydrophobic monomer in a weight ratio of 55-70:15-20:15-20:0.5-3:0.1-1.0; wherein the gel breaker is an ammonium persulfate capsule and/or ammonium persulfate; and wherein the rigid monomer is N-vinyl-2-pyrrolidone and/or sodium p-styrenesulfonate.

8. The method of fracturing stimulation of ultra-high temperature wells according to claim 7, wherein the fluid comprises the following components in mass percentages: 0.6 wt % of the polymeric thickener, 0.015 wt % of the non-metallic crosslinking agent, 0.04 wt % of the gel breaker, and the rest of the fluid is water.

9. The method of fracturing stimulation of ultra-high temperature wells according to claim 7, wherein the non-metallic crosslinking agent is polyethyleneimine.

10. The method of fracturing stimulation of ultra-high temperature wells according to claim 7, wherein the cationic hydrophobic monomer is at least one selected from the group consisting of dimethydiallyllammonium chloride, [2-(Methacryloyloxy)ethyl]trimethylammonium chloride and dimethyl octadecyl allyl ammonium chloride.

11. The method of fracturing stimulation of ultra-high temperature wells according to claim 7, wherein the polymer thickener is prepared by the following method: acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, rigid monomers and cationic hydrophobic monomers are mixed and polymerized at a temperature of 30-40 C. for 8-10 hours to obtain a copolymer; then the copolymer is crushed, dried and finally pulverized.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) To explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the drawings will be briefly described below. Obviously, the drawings in the following description are just some embodiments of the present invention. For those skilled in the art, other drawings may also be obtained based on these drawings without any inventive concepts.

(2) FIG. 1 is a variation curve of the apparent viscosity of the ultra-high temperature fracturing fluid system vs time at 170 s.sup.1 and 180 C.;

(3) FIG. 2 is a variation curve of the apparent viscosity of the ultra-high temperature fracturing fluid system vs time at 170 s.sup.1 and 200 C.;

(4) FIG. 3 is a variation curve of the apparent viscosity of the ultra-high temperature fracturing fluid system vs time at 170 s.sup.1 and 220 C.;

(5) FIG. 4 is a variation curve of the apparent viscosity of the ultra-high temperature fracturing fluid system vs time at 100 s.sup.1 and 220 C.;

(6) FIG. 5 is a variation curve of the apparent viscosity of the ultra-high temperature fracturing fluid system vs time at 100 s.sup.1 and 240 C.;

(7) FIG. 6 is a variation curve of the apparent viscosity of the ultra-high temperature fracturing fluid system vs time of 100 s.sup.1 and 260 C.;

(8) FIG. 7 is a variation curve of apparent viscosity of the guar gum fracturing fluid system vs time at 170 s.sup.1 and 120 C.

DETAILED DESCRIPTION

(9) The specific embodiments of the present invention will be described in detail below with the accompanying drawings.

Embodiment 1

(10) In this embodiment, five monomers of acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, N-vinyl-2-pyrrolidone and dimethyloctadecyl allyl ammonium chloride were polymerized in a weight ratio of 60:20:18:1.5:0.1 at 30 C. for 10 hours to obtain a copolymer, the copolymer was crushed, then dried at 40 C., and finally pulverized to 250 mesh to obtain a polymer thickener powder. The polymer thickener was prepared into a solution with weight percentage of 0.4 wt %, and 0.015 wt % of polyethyleneimine and 0.04 wt % of ammonium persulfate were added to the solution to obtain the fracturing fluid after thorough stirring.

(11) The variation curve of the apparent viscosity of the ultra-high temperature fracturing fluid system over time was tested at 170 s.sup.1 and 180 C., as shown in FIG. 1. It can be seen from FIG. 1, the apparent viscosity of the high temperature fracturing fluid decreases sharply when the temperature increases. When it reaches 180 C., the viscosity is 51 mPa.Math.s, after which, the viscosity rises slowly. Shear continues to be performed to 120 minutes at 180 C., and the viscosity of the high temperature fracturing fluid rises gradually, and the viscosity of the solution reaches 100 mPa.Math.s, indicating that the ultra-high temperature fracturing fluid of the present invention is self-healed, thereby increasing the viscosity of the fracturing fluid system.

Embodiment 2

(12) In this embodiment, five monomers of acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, N-vinyl-2-pyrrolidone and dimethyloctadecyl allyl ammonium chloride were polymerized in a weight ratio of 65:20:15:2.0:0.5 at 35 C. for 10 hours to obtain a copolymer, the copolymer was crushed, and then dried at 40 C., and finally pulverized to 250 mesh to obtain a polymer thickener powder. The polymer thickener was prepared into a solution with weight percentage of 0.4 wt %, and 0.015 wt % of polyethyleneimine and 0.04 wt % of ammonium persulfate were added to the solution to obtain the fracturing fluid after thorough stirring.

(13) The variation curve of the apparent viscosity of the ultra-high temperature fracturing fluid system over time was tested at 170 s.sup.1 and 200 C., as shown in FIG. 2. It can be seen from FIG. 2, the apparent viscosity of the high temperature fracturing fluid decreases sharply when the temperature increases. When it reaches 200 C., the viscosity is 45 mPa.Math.s, after which, the viscosity rises slowly. Shear continues to be performed to 120 minutes at 200 C., and the viscosity of the high temperature fracturing fluid rises gradually, and the viscosity of the solution reaches 80 mPa.Math.s, indicating that the ultra-high temperature fracturing fluid of the present invention is self-healed, thereby increasing the viscosity of the fracturing fluid system.

Embodiment 3

(14) In this embodiment, five monomers of acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, sodium p-styrenesulfonate and [2-(Methacryloyloxy)ethyl]trimethylammonium chloride were polymerized in a weight ratio of 65:17:15:2.0:1.0 at 30 C. for 10 hours to obtain a copolymer, the copolymer was crushed, and then dried at 40 C., and finally pulverized to 20 0 mesh to obtain a polymer thickener powder. The polymer thickener was prepared into a solution with weight percentage of 0.6 wt %, and 0.02 wt % of polyethyleneimine and 0.06 wt % of ammonium persulfate capsule were added to the solution to obtain the fracturing fluid after thorough stirring.

(15) The variation curve of the apparent viscosity of the ultra-high temperature fracturing fluid system over time was tested at 170 s.sup.1 and 220 C., as shown in FIG. 3. It can be seen from FIG. 3, the apparent viscosity of the high temperature fracturing fluid decreases sharply when the temperature increases. When it reaches 220 C., the viscosity is 34 mPa.Math.s. Shear continues to be performed to 120 minutes at 220 C., and the viscosity is maintained at approximately 34 mPa.Math.s, indicating that the thermal destruction of the thickener and the repair of the polyethyleneimine and the thickener achieve a dynamic equilibrium at this point. Therefore, the maximum temperature of the ultra-high temperature fracturing fluid of the present invention is 220 C. at 170 s.sup.1.

Embodiment 4

(16) In this embodiment, six monomers of acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, N-vinyl-2-pyrrolidone, sodium p-styrenesulfonate, and dimethyloctadecyl allyl ammonium chloride were polymerized in a weight ratio of 65:17:15:1.0:1.0:1.0 at 40 C. for 8 hours to obtain a copolymer, the copolymer was crushed, and then dried at 40 C., and finally pulverized to 250 mesh to obtain a polymer thickener powder. The polymer thickener is prepared into a solution with weight percentage of 0.6 wt %, and 0.015 wt % of polyethyleneimine and 0.04 wt % of ammonium persulfate were added to the solution to obtain the fracturing fluid after thorough stirring.

(17) The variation curve of the apparent viscosity of the ultra-high temperature fracturing fluid system over time was tested at 100 s.sup.1 and 220 C., as shown in FIG. 4. It can be seen form FIG. 4, the apparent viscosity of the high temperature fracturing fluid decreases sharply when the temperature increases, and the lowest viscosity drops to 65 mPa.Math.s. Shear continues to be performed to 120 minutes at 220 C., and the viscosity of the high temperature fracturing fluid rises slowly and the viscosity of the solution reaches 120 mPa.Math.s, which indicates that the ultra-high temperature fracturing fluid of the present invention is self-healed, thereby increasing the viscosity of the fracturing fluid system.

Embodiment 5

(18) In this embodiment, six monomers of acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, N-vinyl-2-pyrrolidone, dimethydiallyllammonium chloride and dimethyl octadecyl allyl ammonium chloride were polymerized in a weight ratio of 65:17:15:2.0:0.5:0.5 at 30 C. for 10 hours to obtain a copolymer, the copolymer was crushed, and then dried at 40 C., and finally pulverized to 250 mesh to obtain a polymer thickener powder. The polymer thickener was prepared into a solution with weight percentage of 0.6 wt %, and 0.015 wt % of polyethyleneimine and 0.04 wt % of ammonium persulfate were added to the solution to obtain the fracturing fluid after thorough stirring.

(19) The variation curve of the apparent viscosity of the ultra-high temperature fracturing fluid system over time was tested at 100 s.sup.1 and 240 C., as shown in FIG. 5. It can be seen from FIG. 5, the apparent viscosity of the high temperature fracturing fluid decreases sharply when the temperature increases, and the lowest viscosity drops to 51 mPa.Math.s. Shear continues to be performed to 120 minutes at 240 C., and the viscosity of the high temperature fracturing fluid rises slowly and the viscosity of the solution reaches 124 mPa.Math.s, indicating that the ultra-high temperature fracturing fluid of the present invention is self-healed, thereby increasing the viscosity of the fracturing fluid system.

Embodiment 6

(20) In this embodiment, five monomers of acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, N-vinyl-2-pyrrolidone and dimethyl octadecyl allyl ammonium chloride were polymerized in a weight ratio of 65:17:15:2.0:1.0 at 30 C. for 10 hours to obtain a copolymer, the copolymer was crushed, and then dried at 40 C., and finally pulverized to 250 mesh to obtain a polymer thickener powder. The polymer thickener was prepared into a solution with weight percentage of 0.6 wt %, and 0.015 wt % of polyethyleneimine, 0.02 wt % of ammonium persulfate capsule and 0.02 wt % of ammonium persulfate were added to the solution to obtain the fracturing fluid after thorough stirring.

(21) The variation curve of the apparent viscosity of the ultra-high temperature fracturing fluid system over time was tested at 100 s.sup.1 and 260 C., as shown in FIG. 6. It can be seen from FIG. 6, the apparent viscosity of the high temperature fracturing fluid decreases sharply when the temperature increases. When it reaches 260 C., the viscosity is 30 mPa.Math.s. Shear continues to be performed to 120 minutes at 260 C., and the viscosity is maintained at approximate 35 mPa.Math.s, indicating that the thermal destruction of the thickener and the repair of the polyethyleneimine and the thickener achieve a dynamic equilibrium at this point. Therefore, the maximum temperature of ultra-high temperature fracturing fluid of the present invention is 260 C. at 100 s.sup.1.

(22) Control Group

(23) 0.5 wt % of guar gum solution was prepared, 0.3-0.4 wt % of organ-borate cross-linking agent, 0.02 wt % of ammonium persulfate capsule and 0.02 wt % of ammonium persulfate were added to the guar gum solution, and then stirred thoroughly to obtain a fracturing fluid. The variation curve of the apparent viscosity of the guar gum fracturing fluid system over time was tested at 170 s.sup.1 and 120 C., as shown in FIG. 7. It can be seen from FIG. 7, the apparent viscosity of the high temperature fracturing fluid decreases sharply when the temperature increases. When it reaches 120 C., the viscosity drops to 70 mPa.Math.s. Shear continues to be performed at 120 C., and the viscosity of the fracturing fluid increases slowly and the viscosity of the solution reaches 132 mPa.Math.s, which is caused by the delayed crosslinking of the cross-linking agent. Then the viscosity of the fracturing fluid begins to decrease and eventually maintains at approximate 34 mPa.Math.s, which indicates that the structure of the guar gum fracturing fluid system is destroyed under the thermal shearing action, so the fracturing fluid cannot be applied in reservoirs with temperatures exceeding 120 C.

(24) Although specific embodiments of the present invention have been described in detail, it should not be construed as a limitation on the scope of the patent. Within the scope of the claims, various modifications and alterations made by those skilled in the art without creative labor still belong to the protection scope of the present invention.